/*
 * Copyright 2012-2015 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package lodsve.core.condition;

import java.lang.annotation.Annotation;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Set;

import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.HierarchicalBeanFactory;
import org.springframework.beans.factory.ListableBeanFactory;
import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Condition;
import org.springframework.context.annotation.ConditionContext;
import org.springframework.context.annotation.ConfigurationCondition;
import org.springframework.core.Ordered;
import org.springframework.core.annotation.Order;
import org.springframework.core.type.AnnotatedTypeMetadata;
import org.springframework.core.type.MethodMetadata;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;
import org.springframework.util.MultiValueMap;
import org.springframework.util.ReflectionUtils;
import org.springframework.util.ReflectionUtils.MethodCallback;
import org.springframework.util.StringUtils;

/**
 * {@link Condition} that checks for the presence or absence of specific beans.
 *
 * @author Phillip Webb
 * @author Dave Syer
 * @author Jakub Kubrynski
 * @author Stephane Nicoll
 * @author Andy Wilkinson
 */
@Order(Ordered.LOWEST_PRECEDENCE)
class OnBeanCondition extends SpringBootCondition implements ConfigurationCondition {

    private static final String[] NO_BEANS = {};

    /**
     * Bean definition attribute name for factory beans to signal their product type (if
     * known and it can't be deduced from the factory bean class).
     */
    public static final String FACTORY_BEAN_OBJECT_TYPE = BeanTypeRegistry.FACTORY_BEAN_OBJECT_TYPE;

    @Override
    public ConfigurationPhase getConfigurationPhase() {
        return ConfigurationPhase.REGISTER_BEAN;
    }

    @Override
    public ConditionOutcome getMatchOutcome(ConditionContext context,
                                            AnnotatedTypeMetadata metadata) {
        StringBuilder matchMessage = new StringBuilder();
        if (metadata.isAnnotated(ConditionalOnBean.class.getName())) {
            BeanSearchSpec spec = new BeanSearchSpec(context, metadata,
                    ConditionalOnBean.class);
            List<String> matching = getMatchingBeans(context, spec);
            if (matching.isEmpty()) {
                return ConditionOutcome
                        .noMatch("@ConditionalOnBean " + spec + " found no beans");
            }
            matchMessage.append("@ConditionalOnBean ").append(spec)
                    .append(" found the following ").append(matching);
        }
        if (metadata.isAnnotated(ConditionalOnMissingBean.class.getName())) {
            BeanSearchSpec spec = new BeanSearchSpec(context, metadata,
                    ConditionalOnMissingBean.class);
            List<String> matching = getMatchingBeans(context, spec);
            if (!matching.isEmpty()) {
                return ConditionOutcome.noMatch("@ConditionalOnMissingBean " + spec
                        + " found the following " + matching);
            }
            matchMessage.append(matchMessage.length() == 0 ? "" : " ");
            matchMessage.append("@ConditionalOnMissingBean ").append(spec)
                    .append(" found no beans");
        }
        return ConditionOutcome.match(matchMessage.toString());
    }

    private List<String> getMatchingBeans(ConditionContext context,
                                          BeanSearchSpec beans) {
        ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();
        if (beans.getStrategy() == SearchStrategy.PARENTS) {
            BeanFactory parent = beanFactory.getParentBeanFactory();
            Assert.isInstanceOf(ConfigurableListableBeanFactory.class, parent,
                    "Unable to use SearchStrategy.PARENTS");
            beanFactory = (ConfigurableListableBeanFactory) parent;
        }
        if (beanFactory == null) {
            return Collections.emptyList();
        }
        List<String> beanNames = new ArrayList<String>();
        boolean considerHierarchy = beans.getStrategy() == SearchStrategy.ALL;
        for (String type : beans.getTypes()) {
            beanNames.addAll(getBeanNamesForType(beanFactory, type,
                    context.getClassLoader(), considerHierarchy));
        }
        for (String ignoredType : beans.getIgnoredTypes()) {
            beanNames.removeAll(getBeanNamesForType(beanFactory, ignoredType,
                    context.getClassLoader(), considerHierarchy));
        }
        for (String annotation : beans.getAnnotations()) {
            beanNames.addAll(Arrays.asList(getBeanNamesForAnnotation(beanFactory,
                    annotation, context.getClassLoader(), considerHierarchy)));
        }
        for (String beanName : beans.getNames()) {
            if (containsBean(beanFactory, beanName, considerHierarchy)) {
                beanNames.add(beanName);
            }
        }
        return beanNames;
    }

    private boolean containsBean(ConfigurableListableBeanFactory beanFactory,
                                 String beanName, boolean considerHierarchy) {
        if (considerHierarchy) {
            return beanFactory.containsBean(beanName);
        }
        return beanFactory.containsLocalBean(beanName);
    }

    private Collection<String> getBeanNamesForType(ListableBeanFactory beanFactory,
                                                   String type, ClassLoader classLoader, boolean considerHierarchy)
            throws LinkageError {
        try {
            Set<String> result = new LinkedHashSet<String>();
            collectBeanNamesForType(result, beanFactory,
                    ClassUtils.forName(type, classLoader), considerHierarchy);
            return result;
        } catch (ClassNotFoundException ex) {
            return Collections.emptySet();
        }
    }

    private void collectBeanNamesForType(Set<String> result,
                                         ListableBeanFactory beanFactory, Class<?> type, boolean considerHierarchy) {
        result.addAll(BeanTypeRegistry.get(beanFactory).getNamesForType(type));
        if (considerHierarchy && beanFactory instanceof HierarchicalBeanFactory) {
            BeanFactory parent = ((HierarchicalBeanFactory) beanFactory)
                    .getParentBeanFactory();
            if (parent instanceof ListableBeanFactory) {
                collectBeanNamesForType(result, (ListableBeanFactory) parent, type,
                        considerHierarchy);
            }
        }
    }

    private String[] getBeanNamesForAnnotation(
            ConfigurableListableBeanFactory beanFactory, String type,
            ClassLoader classLoader, boolean considerHierarchy) throws LinkageError {
        String[] result = NO_BEANS;
        try {
            @SuppressWarnings("unchecked")
            Class<? extends Annotation> typeClass = (Class<? extends Annotation>) ClassUtils
                    .forName(type, classLoader);
            result = beanFactory.getBeanNamesForAnnotation(typeClass);
            if (considerHierarchy) {
                if (beanFactory
                        .getParentBeanFactory() instanceof ConfigurableListableBeanFactory) {
                    String[] parentResult = getBeanNamesForAnnotation(
                            (ConfigurableListableBeanFactory) beanFactory
                                    .getParentBeanFactory(),
                            type, classLoader, true);
                    List<String> resultList = new ArrayList<String>();
                    resultList.addAll(Arrays.asList(result));
                    for (String beanName : parentResult) {
                        if (!resultList.contains(beanName)
                                && !beanFactory.containsLocalBean(beanName)) {
                            resultList.add(beanName);
                        }
                    }
                    result = StringUtils.toStringArray(resultList);
                }
            }
            return result;
        } catch (ClassNotFoundException ex) {
            return NO_BEANS;
        }
    }

    private List<String> getPrimaryBeans(ConfigurableListableBeanFactory beanFactory,
                                         List<String> beanNames) {
        List<String> primaryBeans = new ArrayList<String>();
        for (String beanName : beanNames) {
            BeanDefinition beanDefinition = beanFactory.getBeanDefinition(beanName);
            if (beanDefinition != null && beanDefinition.isPrimary()) {
                primaryBeans.add(beanName);
            }
        }
        return primaryBeans;
    }

    private static class BeanSearchSpec {

        private final Class<?> annotationType;

        private final List<String> names = new ArrayList<String>();

        private final List<String> types = new ArrayList<String>();

        private final List<String> annotations = new ArrayList<String>();

        private final List<String> ignoredTypes = new ArrayList<String>();

        private final SearchStrategy strategy;

        BeanSearchSpec(ConditionContext context, AnnotatedTypeMetadata metadata,
                       Class<?> annotationType) {
            this.annotationType = annotationType;
            MultiValueMap<String, Object> attributes = metadata
                    .getAllAnnotationAttributes(annotationType.getName(), true);
            collect(attributes, "name", this.names);
            collect(attributes, "value", this.types);
            collect(attributes, "type", this.types);
            collect(attributes, "annotation", this.annotations);
            collect(attributes, "ignored", this.ignoredTypes);
            collect(attributes, "ignoredType", this.ignoredTypes);
            this.strategy = (SearchStrategy) metadata
                    .getAnnotationAttributes(annotationType.getName()).get("search");
            BeanTypeDeductionException deductionException = null;
            try {
                if (this.types.isEmpty() && this.names.isEmpty()) {
                    addDeducedBeanType(context, metadata, this.types);
                }
            } catch (BeanTypeDeductionException ex) {
                deductionException = ex;
            }
            validate(deductionException);
        }

        protected void validate(BeanTypeDeductionException ex) {
            if (!hasAtLeastOne(this.types, this.names, this.annotations)) {
                String message = annotationName()
                        + " did not specify a bean using type, name or annotation";
                if (ex == null) {
                    throw new IllegalStateException(message);
                }
                throw new IllegalStateException(message + " and the attempt to deduce"
                        + " the bean's type failed", ex);
            }
        }

        private boolean hasAtLeastOne(List<?>... lists) {
            for (List<?> list : lists) {
                if (!list.isEmpty()) {
                    return true;
                }
            }
            return false;
        }

        protected String annotationName() {
            return "@" + ClassUtils.getShortName(this.annotationType);
        }

        protected void collect(MultiValueMap<String, Object> attributes, String key,
                               List<String> destination) {
            List<?> values = attributes.get(key);
            if (values != null) {
                for (Object value : values) {
                    if (value instanceof String[]) {
                        Collections.addAll(destination, (String[]) value);
                    } else {
                        destination.add((String) value);
                    }
                }
            }
        }

        private void addDeducedBeanType(ConditionContext context,
                                        AnnotatedTypeMetadata metadata, final List<String> beanTypes) {
            if (metadata instanceof MethodMetadata
                    && metadata.isAnnotated(Bean.class.getName())) {
                addDeducedBeanTypeForBeanMethod(context, metadata, beanTypes,
                        (MethodMetadata) metadata);
            }
        }

        private void addDeducedBeanTypeForBeanMethod(ConditionContext context,
                                                     AnnotatedTypeMetadata metadata, final List<String> beanTypes,
                                                     final MethodMetadata methodMetadata) {
            try {
                // We should be safe to load at this point since we are in the
                // REGISTER_BEAN phase
                Class<?> configClass = ClassUtils.forName(
                        methodMetadata.getDeclaringClassName(), context.getClassLoader());
                ReflectionUtils.doWithMethods(configClass, new MethodCallback() {
                    @Override
                    public void doWith(Method method)
                            throws IllegalArgumentException, IllegalAccessException {
                        if (methodMetadata.getMethodName().equals(method.getName())) {
                            beanTypes.add(method.getReturnType().getName());
                        }
                    }
                });
            } catch (Throwable ex) {
                throw new BeanTypeDeductionException(
                        methodMetadata.getDeclaringClassName(),
                        methodMetadata.getMethodName(), ex);
            }
        }

        public SearchStrategy getStrategy() {
            return (this.strategy != null ? this.strategy : SearchStrategy.ALL);
        }

        public List<String> getNames() {
            return this.names;
        }

        public List<String> getTypes() {
            return this.types;
        }

        public List<String> getAnnotations() {
            return this.annotations;
        }

        public List<String> getIgnoredTypes() {
            return this.ignoredTypes;
        }

        @Override
        public String toString() {
            StringBuilder string = new StringBuilder();
            string.append("(");
            if (!this.names.isEmpty()) {
                string.append("names: ");
                string.append(StringUtils.collectionToCommaDelimitedString(this.names));
                if (!this.types.isEmpty()) {
                    string.append("; ");
                }
            }
            if (!this.types.isEmpty()) {
                string.append("types: ");
                string.append(StringUtils.collectionToCommaDelimitedString(this.types));
            }
            string.append("; SearchStrategy: ");
            string.append(this.strategy.toString().toLowerCase());
            string.append(")");
            return string.toString();
        }

    }

    static final class BeanTypeDeductionException extends RuntimeException {

        private BeanTypeDeductionException(String className, String beanMethodName,
                                           Throwable cause) {
            super("Failed to deduce bean type for " + className + "." + beanMethodName,
                    cause);
        }

    }

}
